In general, an eco-friendly vehicle such as a pure electric vehicle (EV) or a hybrid electric vehicle (HEV) is driven using an electric motor as a driving source.
The pure EV is driven only using power of the electric motor that operates by battery power, and the HEV is driven by efficiently combining power of an engine and power of the electric motor.
Other examples of the eco-friendly vehicle may include a fuel cell electric vehicle (FCEV) which is driven by operating an electric motor using power generated from a fuel cell.
The FCEV is also a vehicle which is driven using an electric motor, and may be broadly classified as the EV, which is driven by electric power, together with the pure EV and the HEV.
FIG. 1 illustrates a system configuration of the EV. As illustrated in the figure, a driving motor (MG1) 13 and a drive shaft are mechanically connected to each other, and the EV includes a motor control unit (MCU) 17 including an inverter 16 for driving and controlling the driving motor 13, a high-voltage battery 18 for supplying driving power to the driving motor 13, and a battery management system (BMS) 19 for controlling the battery 18.
Here, the battery 18 functions as a driving source (power source) of the vehicle and is connected to the driving motor 13 through the inverter 16 in a chargeable and dischargeable manner, and the inverter 16 inverts a direct current of the battery 18 into three-phase alternating current and applies the inverted current to the driving motor 13 in order to drive the driving motor 13.
The BMS 19 collects battery state information such as a voltage, a current, a temperature, a state of charge (SOC) (%), etc. of the battery 18. Here, the BMS 19 provides the collected battery state information to another controller in the vehicle, or directly participates in control of battery charging and discharging using the battery state information.
FIG. 2 illustrates a system configuration of the HEV, and illustrates a power train configuration using a transmission mounted electric device (TMED) in which a transmission 14 is disposed at an output side of a driving motor 13.
As illustrated in the figure, the HEV includes an engine 11 and the driving motor 13 disposed in series to function as driving sources for vehicle driving, an engine clutch 12 disposed between the engine 11 and the driving motor 13 to connect or block power, the transmission 14 for shifting power of the engine 11 and the driving motor 13 and transferring the shifted power to a drive shaft, and a starter-generator (MG2) 15 directly connected to the engine 11 to be able to transfer power.
The engine clutch 12 connects or blocks power between two driving sources, that is, the engine 11 and the driving motor 13 that drive the vehicle through a locking-up or opening operation.
In addition, a battery 18 that functions as a power source of the vehicle is connected to the driving motor 13 and the starter-generator 15 in a chargeable and dischargeable manner through an inverter 16. The inverter 16 inverts a direct current of the battery 18 into a three-phase alternating current and applies the inverted current to the driving motor 13 and the starter-generator 15 in order to drive the driving motor 13 and the starter-generator 15.
The starter-generator 15 performs an integrated function of a starter motor and a generator. The starter-generator 15 starts the engine 11 by transferring power thereof to the engine 11 through a power transmission mechanism (for example, a belt and a pulley) when driving or generates power by receiving a rotating force transferred from the engine 11, and charges the battery 18 with electric energy generated during a generation operation.
However, in the above-described conventional eco-friendly vehicle, is disadvantageous in that mechanical damping effect of an existing torque converter cannot be acquired.
Therefore, there has been a problem of degrading comfort and operability due to a vibration phenomenon such as shock or jerk (instantaneous and rapid motion) together with occurrence of vibration of a drive shaft when a speed is changed, when a tip-in/out operation (operation of pressing or releasing an accelerator pedal) is performed and when an engine clutch is defective, etc.
That is, vibration from a torque source (engine or motor) or vibration from the outside is rarely attenuated since a damper disposed between the torque source and a driving system is small not being used.
A vibration component of the drive shaft needs to be extracted to reduce vibration occurring from the drive shaft. Vibration reduction performance varies according to accuracy of extraction of the vibration component, and thus, it is important to accurately extract the vibration component.
In a conventional anti-jerk control technology as a method of suppressing vibration of a drive shaft for solving the above-mentioned problem, a deviation between a model velocity and an actual velocity of a motor is recognized as vibration, the deviation between the velocities is multiplied by a certain value, and the multiplied value is fed back, thereby suppressing vibration.
For example, an apparatus and a method for controlling anti-jerk have been studied, in which a reference velocity deviation and a velocity deviation average value are calculated from a velocity deviation between a model velocity and an actual velocity of a motor, whether vibration occurs from a drive shaft is determined. A magnitude of a torque for motor correction for anti-jerk used to reduce vibration of the drive shaft is calculated to control a motor torque when vibration is determined to occur from the drive shaft.
In the technology, an ideal model for the drive shaft, that is, a model capable of calculating an ideal velocity (model velocity) of the drive shaft which ignores vibration is designed, and a net torque of the drive shaft obtained by subtracting a drag torque from a motor torque instruction is input to the model, thereby obtaining a velocity of the drive shaft excluding a vibration component (hereinafter referred to as a model velocity).
Here, the model for calculating the model velocity cannot accurately consider a load torque, etc. generated in an actual vehicle, and thus, a calculated model velocity contains an error. In order to correct the error, a difference between the model velocity and the actual velocity of the motor is multiplied by a certain gain value to calculate a correction torque, and then the net torque of the drive shaft is corrected.
However, correction is performed only when the difference between the model velocity and the actual velocity is present, and thus, accuracy is low.
In addition, a method and a system for controlling anti-jerk have been studied, in which a model velocity is calculated using a velocity of a wheel which is mechanically connected to a driving motor.
When a model velocity is calculated using a velocity of a wheel as described above, it is possible to accurately calculate the model velocity since a load applied to the wheel is great, and thus, vibration occurring from a drive shaft is attenuated.
In addition, the model velocity may be accurately calculated since the wheel velocity is a component generated by attenuation of vibration of the drive shaft. A load factor is low since the model velocity is calculated using only signal processing for the wheel velocity.
However, even when the wheel is mechanically connected to the drive shaft, the wheel velocity is delayed when compared to a velocity of the drive shaft in a dynamical relation. When a vehicle state rapidly changes, for example, when a vehicle is accelerated or decelerated, a delay component may increase, and thus, an erroneous vibration component may be extracted.
When the vibration component is erroneously extracted due to the above-described delay, a compensation torque for reducing vibration determined by the erroneously extracted vibration component may be output such that acceleration/deceleration of the vehicle is impeded.
A method of obtaining a model velocity has been developed, in which an ideal model is designed for a drive shaft, and a calculated net torque of the drive shaft is inputted into the model.
Here, an error contained in the obtained model velocity is presumed to be an error generated by a disturbance torque applied to a vehicle. After the error is estimated, the disturbance torque is compensated by a net torque component of the drive shaft to calculate the model velocity.
Therefore, it is possible to more accurately calculate a model velocity when compared to an existing model velocity calculation scheme using a torque.
The disturbance torque is calculated by inputting a measured drive shaft velocity to a reciprocal of a designed drive shaft model to estimate a torque input to the drive shaft, and then comparing the estimated torque with the input net torque of the drive shaft.
In a reciprocal of a transfer function of the drive shaft model, an order of the numerator may be greater than an order of the denominator, which corresponds to differentiation in a mathematical sense. When the transfer function is used, noise of a signal of the measured drive shaft velocity occurs.